interface CompurerAverage {
    public double average(double a,double b);
}
class A implements CompurerAverage {
    public double average(double a,double b){
	double aver=0;
	aver=(a+b)/2;
	return aver;
    }
}
class B implements CompurerAverage {
    public double average(double a,double b){
	double aver=0;
	aver= Math.sqrt(a*b);
	return aver;
    }
}
public class Example6_4 {
    public static void main(String args[]) {
	CompurerAverage computer;
	double a=11.23,b=22.78;
	computer=new A();
	double result=computer.average(a,b);
	System.out.printf("%5.2f和%5.2f的算数平均值：%5.2f\n",a,b,result);
	computer=new B();
	result=computer.average(a,b);
	System.out.printf("%5.2f和%5.2f的几何平均值：%5.2f",a,b,result);
    }
}
